The Rainforest: Yes, It may be Copied

Geo. W. Thorpe

Who, having ventured deep into a rainforest for the first time, could fail but be captivated by the sheer overwhelming power of the scene, even sensing a feeling of oppression as the abundance of life forms closes in around one. The sight of so many tall trees, their trunks forming the framework of the rainforest as they stand so close together, some with gigantic buttresses, others straight stemmed and varying little in girth from ground to topmost branch, is surely a magnificent and awe-inspiring experience. But then stand still and observe that, as well as the trees, there are ferns, epiphytes, mosses, fungi and small plants, some growing at ground level, others clinging to tree trunks and branches or merging into the green canopy above, and the spectacle makes one wonder how the earth can support and sustain such a weight of living material in an area so small.

Here. deep in the forest, with so much vegetation blotting out the outside world, and only soft filtered light penetrating the canopy, is a retreat of solitude and tranquillity such as can be found in few other places.

How then can we bring more people to the realisation that, just as the rainforest can be used for relaxation and interest, it needs understanding to ensure its continued survival. The simple answer is to make more rainforest visible to more people by bringing it closer to them. Hence my reason for encouraging the creation of rainforest plantations within home gardens and project areas, so that people and the rainforest can both survive. Note that I don't enthuse about the growing of individual rainforest plants as specimen subjects. I can tolerate that use, but as my love is for the rainforest as an entity, I always see an isolated plant as lonely and longing for the company of its own kind.

A suburban rainforest - is it for you?

Lest our impassioned pleas encourage the over enthusiastic approach to the growing of rainforest plants, I think it is only fair to point out that there are some disadvantages. Firstly the work angle, and even though a visit to a well-established rainforest garden may evoke the observation, "well, here is a real minimum-care garden, no lawn, no weeds, no pruning, no spraying, nothing to do but enjoy and encourage the exuberant efforts of Mother Nature," there is a "but". However, you as keen gardeners will know that a lot of work has to go into the initial preparation of any garden, and in order that a recognisable rainforest may be produced a tremendous amount of work is usually necessary. In four or five years time, and I think that's long enough to wait to enjoy the fruits of one's labour, the work content will have dwindled to almost zero, and the enjoyment soared to great heights.

Unlike a "normal" garden, a rainforest plot does not become "leggy" or sprawling with age. Its character is permanence, as growth is upward. where space is abundant and age serves only to add usefulness. Tree trunks and branches become robust enough to accommodate epiphytic orchids and ferns, and the canopy reaches the right height for nesting and roosting birds. Under natural rainforest conditions trees grow for perhaps a hundred, or maybe hundreds of years, until they reach maturity then die and decay on the spot to provide food for those that remain, so the cycle goes on "ad infinitum". Only a rainforest tree can be a thing of beauty during the decay phase, as any rainforest enthusiast will testify.

Tall trees in a suburban allotment scare the wits out of some people, and particularly in Queensland where we're liable to receive winds of cyclonic force, it can be argued that tall trees are a potential hazard. The reason for the abhorrence of tall plants by some people is, I think, rooted in the idea that humans are the dominant creatures on the earth and must be able to stand above their garden and look down on their subjects. Just as some people feel claustrophobic when taken deep into a rainforest, so some people cannot tolerate a garden in which humans are insignificant and the plants dominate the scene.

A further benefit from a rainforest garden is the reduction in temperature which results from the micro climate produced by the rainforest plot itself. In summer this is very welcome, and within our own backyard rainforest I have regularly measured temperatures of five to ten degrees celcius below ambient on very hot days. It is certainly conceivable that we could reduce the temperature of large tracts of suburbia if sufficient people could be induced to follow the rainforest plan.

Plants for the urban rainforestClick on thumbnail images or plant names for larger images

A rainforest plot may not be considered to have the eye appeal of a well laid out, landscaped, log-edged, bark-chip mulched bed of healthy vigorous flowering grevilleas, melaleucas, callistemons, etc. As opposed to this the enjoyment of a rainforest garden is the opportunity it provides to stand within the garden completely enshrouded by masses of vegetation. Here the pleasure is in the feeling of total absorption within a soft green mantle enhanced by the subtle intermingling of various leaf shapes, colours and patterns, and the play of sun and shadow through the canopy above, all of which combines to generate feelings of harmony and tranquillity.

Repeatedly, visitors to our backyard rainforest plot express the feeling as "gee, isn't it peaceful in here, you'd never know you were in a city". Isn't it ominous, people always associate the bush with peace, never the city! But it is wonderful to be able to provide yourself and your visitors with marvellous tranquillity and a breathing space away from city pressures just by judicious use of the right plants in the right situation, and isn't that what gardening is all about?

One characteristic of rainforest plants in a rainforest situation which may be a disadvantage to some people is the paucity of flowers on plants which in an open situation may flower profusely. Hymenosporum flavum, the so-called native frangipani, provides a good example of this phenomenon. In open sunny situations I have seen it remain for years as a tall-growing shrub or small tree with branches and leaves to ground level, and in season smothered in creamy yellow sweet-scented flowers. However, in our rainforest Hymenosporum flavum in five years has grown to 10 m, with a slender trunk 10cm in diameter, on which the lower branches in turn die and are shed, leaving a long bare trunk with leaves only on the few topmost branches. It still flowers, but the flowers are quite remote and unnoticed. This is often the style of rainforest trees, particularly in well-established situations.

First steps

Before deciding to establish a rainforest garden there is a need to ensure that sufficient space is available, and an area of 16 square metres is probably the minimum size in which desirable results can be achieved. Remember, I prefer to see rainforest plants used in as authentic a rainforest situation as possible. Just as we would, for very good reasons, if deciding to construct a semi-arid garden keep the appropriate plants together and not scattered among other more tolerant plants, so for those same good reasons I like to see rainforest plants in company with their own kin.

Our home rainforest site was most inhospitable, being a few centimetres of poor topsoil derived from Brisbane metamorphic shale, which has little to recommend it except that tree roots are able to force their way into its fissures and gain a firm footing, but nothing else. It is a south-west facing slope, and that in Brisbane means that in winter it receives all the icy blasts from Hobart via Melbourne, and the cold dry westerly winds from the interior, but in summer it has some advantages because we avoid the full effect of the sun and get shelter from the hot drying north-west winds.

There were no humps or hollows on the site, so our first moves were to throw up contour banks, which of course slow up water runoff, but more importantly for rainforest production stop organic material from being carried away. As the top soil was so scarce and of such poor texture we knew that rainforest plants would not flourish until soil quality had been vastly improved.

Plants for the urban rainforestClick on thumbnail images or plant names for larger images

It is a popular notion that rainforest land is inherently fertile, and this misconception in the past was. and probably still is, the reason why rainforest was and is being felled to make way for agricultural pursuits. The truth is that rainforest creates its own fertility through the decay of organic material (the original organic garden), hence the ability of rainforest to flourish on pure white sand in places such as Fraser Island and Cooloola in Queensland, and on extremely rocky places in other areas. But the mystery to me is how in nature the first rainforest plants know when it's time to establish themselves. We know that areas which are now rainforest covered must have begun their soil/plant relationship with very hardy species, slowly building up through a succession of varying species, until such time as pioneer rainforest species appeared. As conditions became more suitable more rainforest species would have arrived on the scene, and eventually the complex rainforest community that we see today would have evolved.

Well we, of course, had to short circuit this procedure, and knowing that organic material is the key to success we arranged to collect all the "waste" lawn clippings, raked leaves, prunings, etc., from all the homes around us. I even mowed and scythed vacant allotments in the neighbourhood, much to the bewilderment of locals, who thought I was either mad or uncommonly civic-minded, or both.

After months of organic matter collection, and repeated heavy applications of a 15:3:10 fertilizer, soil texture began to improve and the earthworm population exploded. During these early days we made preparation for our rainforest by planting a complete external shelter belt of non-rainforest hardy species, including Casuarina glauca, Acacia fimbriala, A.spectabilis, A.podalyrlitolia and A.cunninghamii, Grevillea pferidifolia, G.hodgei, G.banksii, Eucalyptus tereticornis, Hakea florulenfa, H.gibbosa, as well as Callistemon pachyphyllus and C.polandii - all species able to withstand sun and wind and tall enough to force the young rainforest plants upwards.

That is what we did, but with the benefit of hindsight we now know that we could have avoided the use of non-rainforest plants by using a group of rainforest plants which are, or can be. pioneer species, and under the good conditions provided would have been perhaps more effective as a shelter belt. I refer to plants in the family Sapindaceae such as Alectryon, Cupaniopsis, Sarcopteryx, Jagera, Toechima, Ellatostachys, and Harpullia. Other hardy rainforest plants may be found in the family Euphorbiaceae and include the genera Glochidion, Baloghia, Crofon, Mallotus, Macaranga and Omalanthus. Other genera which are hardy enough to use as initial planting material include Alphitonia, Aphananihe, Trema, Streblus and Ficus; also we could include genera from the family Celastraceae such as Mayienus, Denhamia and Elaeodendron. The list could go on and on, but those plants mentioned are ones whose seed is usually available in sufficient quantity to provide material to "wall" in any area selected for a rainforest plantation. Propagation material for some of the rainforest species may present supply problems, but at least in Queensland we have organised a small group of enthusiasts who regularly exchange plants and seeds.

Choice of plants

Having defined the edges of the rainforest, thought may then be given to the body of the rainforest, where the choice of plants is limitless. Plants growing in our own rainforest which have responded to garden culture, in addition to those previously mentioned, include the following:

Plant Family

Plant Selections

Pittosporaceae

Several Pittosporum species and Hymenosporum flavum

Verbenaceae

Clerodendron tomenfosum, Gmelina leichhardtii and Premna lignum-vitae

Oleaceae

The fast-growing Olea panicula

Araliaceae

Delarbrea
michieana, Tioghemopanax elsgans and the best known of our rainforest trees, the ever-popular umbrella tree, Schefflera actinophylla

Myrtaceae

A big group of our plants comes from this family and includes several Syzygium species, Rhodamnia trinervia, two Pilidiostigma species, two Backhousia species, the very beautiful 'Golden Penda', Xanthostemon chrysantha, and the equally delightful Tristaniopsis laurina.

Sterculiaceae

This family is represented by Sterculia quadrifida, the interesting 'peanut tree' with edible seeds, the flamboyant 'flame tree', Brachychiton acerifolium, trees with attractive foliage, Argyrodendron species and Commersonia bartramia.

This family gives us the golden-flowered Barklya syringifolia and the well-known 'Moreton Bay chestnut' or 'black bean', Castanospermum australe.

Caesalpinaceae

This family has the rainforest Cassia species.

Mimosaceae

Those plants with delightful white and pink pom-pom flowers and spiral seed
capsules, the Archidendron species.

Cunoniaceae

This family has given us the attractive foliaged Ackama panicu!ata and the plant which was the original wattle of Port Jackson days, Callicoma serratifolia.

Escalloniaceae

This family is represented by the low-growing tree of the gullies, Cuttsia viburnea, by the rare and extremely beautiful Anopterus macleayanus and the delightful small tree
Polyosma cunninghamii.

Lauraceae

From this family we have taken Neolitsea dealbata and Cryptocarya glaucescens.

Proteaceae

This gives us the rainforest Grevillea species and the well-known 'wheel of fire', Stenocarpus sinuatus.

Several additional species have come from minor families, and as we explore further we find more and more plants that demand attention.

Climate requirements

Two things I haven't mentioned are the requirements of climate and water. Both are important, but just how important I am not in a position to speak positively. Suffice to say that as all the rainforest species which I have utilised and mentioned come from the sub-tropical areas, it's reasonable to assume that they would fail in cold climates.

Experience in Canberra, however, has proved otherwise, but of course there the site for the rainforest was carefully chosen, and climate has been modified. Such work could be done in other places, and I'm sure that we in Queensland would be only too happy to assist in whatever was necessary to see that a project started in what should be, according to the rules, a hostile rainforest situation, could become a useful and valuable exercise.

Water is necessary to a rainforest, but is not the "be all", and as I mentioned earlier the better term for rainforest is closed forest. Rainforest type communities occur naturally in areas of quite low rainfall, but of course under garden situations we can usually adjust water application to best suit the needs of the plants. The ideal for a constructed rainforest garden is a sprinkler system with mist-type spray nozzles, for to keep a rainforest looking its best it's more important to keep the leaves damp than the ground wet; the sprinklers therefore should be set as high in the canopy as possible and rise as it rises. Added bonuses available with a good watering system are the ferns, vines, epiphytes, etc., earlier mentioned, which of course make the rainforest garden into a true green paradise.

Maintaining your rainforest

Tracks are important in a rainforest garden and should be planned in the early stages. They must allow for free movement through the rainforest, but be routed carefully to avoid trampling sensitive areas. We continually throw chopped-up organic material around our tracks to counter the compacting effect of pedestrians, and that does seem to alleviate the problem. The chopped material is produced in an old hand-powered chaffcutter, which is one of the most valuable tools we have. It accepts all prunings, even quite thick stems and reduces a bulky heap to manageable proportions in quick time.

Plants for the urban rainforestClick on thumbnail images or plant names for larger images

We now use a 10:2:8 fertilizer (General Fertilizers 'Sulphapine') broadcast four times a year at an annual rate of 1 kg to 6 sq. m. This rate may seem excessive, but when you contemplate the amount of living material which occupies each of those 6 sq. m then it really is reasonable.

After six years of growth . . . leaf and litter drop in our rainforest almost maintains a sufficient amount of organic material, but the rate at which it is converted to a beautiful friable soil mixture by earthworms and bacteria is incredible. The original 5cm of poor topsoil has now grown to 30cm or more of high-grade material, and the process continues.

As the rainforest develops, and tree trunks increase in length, there is a danger that the floor of the rainforest will become exposed to too much sun and wind. To combat this natural progression we have planted low-growing shrubs around the edge, and within the rainforest, to maintain the closed-in condition. For this duty plants of the genera Citriobatus, Capparis and Carissa have proved their worth. They are all thorny and provide an ideal cover for small birds in their ceaseless efforts to avoid predators. We have found that our rainforest is the night quarters for dozens of birds of varying species and our feathered friends sing our praises all day long.

Rainforest is a fascinating part of our ecological system, and I feel that if preservation of the flora is one of our major activities then with even a small rainforest plot we can both enjoy the "feel" of rainforest and at the same time help to preserve a very great number of rainforest species.

From Australian Plants, journal of the Association of Societies for Growing Australian Plants, September 1978.